The electrical requirements for the automotive, truck, boat and recreational vehicle industry have, with few exceptions, become standardized using twelve volt direct current (DC) electrical systems and using one or more twelve volt batteries wired in parallel for storage. Most vehicles have twelve volt lights, twelve volt starter motor and twelve volt ancillary motors for such things as windshield wipers, electric door locks and power windows. The twelve volt systems work well and twelve volt fractional horsepower motors are ideal for intermittent use as the current draw for these small motors is not great. Twelve volt engine starter motors produce very high torque for engine starting, but at a very high current draw, often in the range of 400 amperes per hour. These motors can only run for a few minutes before they drain the vehicle battery bank and/or burn up.
The twelve volt base electrical systems in vehicles have precluded the development of practical and efficient electrically driven equipment such as air compressors, hydraulic pumps, air conditioners and vacuum systems to be mounted on service, recreational, or over the road vehicles. As an example: If a service truck requires an air compressor for inflating tires, or running air tools, the compressor is invariably driven by an internal combustion engine. The engine requires much maintenance, is expensive to run and emits pollutants into the atmosphere. Twelve volt DC motors draw far too much current to make such a compressor a viable portable option for a continuous air supply.
Hydraulic systems for tow trucks and auxiliary hydraulic power take-offs are driven by pumps that the vehicle engine powers, or by auxiliary internal combustion engines mounted on the vehicle. Such engine-powered hydraulic pumps for equipment like hydraulic lifts, or hydraulic chain saws are lighter, safer and easier to use than their internal combustion engine counterparts. However, an internal combustion engine must be running all the time and they are loud and dirty and high maintenance items.
Owing to new electric motor technology developed over the past decade, a plethora of electric motor types have been developed to deliver very high torque at a small fraction of the current draw of direct DC, 12 volt motors, in part because higher voltage motors draw fewer amps (Ohm's Law, (I=V/R)). Motors such as “brushless DC” and 48 volt AC motors are becoming common in industry for such things as golf carts and fork lift trucks, but they are based on a forty-eight volt platform requiring battery chargers to run from a 110/220 volt ac power source. No satisfactory system exists that allows high torque, 24, 36 or 48 volt motors to be run from a 12 volt source.